Fustomer is an amalgam of the words Fuss or Fussy and Customer. Generaly a phrase used by those working in the service industry to denote a customer who makes unreasonable requests or complains about things that other people have no problem with. Nine times out of ten a fustomer will be an over 50 year old suffering from an engourged sense of entitlement.

Did you see that fustomer getting all up in my face because he had to cue for five minutes? He didnt seem to mind making the people behind him wait even longer just because he wanted to argue with someone